1. Field of the Invention
This invention relates to movable stages and other precision location mechanisms and more particularly to a stage with multiple rotating tables on air bearings.
2. Description of Related Art
Movable stage systems are typically used in many applications where precise two-dimensional movement is required to position an object supported on a stage, e.g., in high resolution lithography applications. Such movable stages typically progress linearly on linear races and bearings and are conventionally driven along both the X and Y axes. Typically this is accomplished by linear motors or actuators; a first set of linear actuators providing the X direction motion and a second set of linear actuators providing the orthogonal Y direction motion. For instance, the stage powered by linear motors may be moved back and forth in the Y direction on a mechanical guide beam which in turn is moved and powered by linear motors in the X direction along guide rails. This provides the desired independent two direction motion.
Such a stage supports, for instance, a mask blank or other workpiece so that the workpiece is precisely positioned for lithography. Similar arrangements are used in other lithographic applications, for instance, for defining conductive patterns on a laminate workpiece which is a substrate for a printed circuit board. Typically, a chuck is located on a stage or other holding mechanism arrangement for holding the workpiece. Conventional stages used for electron beam lithographic applications present several problems because they typically require the use of bellows, thin gap seals, or other mechanisms operating inside a vacuum to enclose the electron beam. Some of these problems include limited stage travel, vibration from the bellows, and poor positioning resolution partly due to thermal expansion of materials such as the guide rails or holding mechanisms heated up by the motors. Therefore, there is a need for a movable stage having minimal vibration with smooth and large effective travel, useful but not limited to electron beam lithography applications.